A vehicle such as an electric vehicle (EV) and a plug-in hybrid vehicle (PHV) is equipped with a rechargeable battery as an electrical storage device that stores a power supply to a motor for running the vehicle. Some rechargeable batteries have a case that accommodates an electrode assembly. The case is formed by welding a case body and a lid to each other. An electrode terminal is electrically connected to the electrode assembly accommodated in the case body. The body of the electrode terminal is cylindrical. The electrode terminal is arranged to pass through a through hole of the lid and protrudes from the inside to the outside of the case body. An insulating distance is ensured in a gap between the inner circumferential surface of the through hole and the outer circumferential surface of the electrode terminal, which faces the inner circumferential surface. A sealing structure of the above gap is provided in the rechargeable battery. For example, refer to Patent Document 1.
As shown in FIG. 13, a battery 80 of Patent Document 1 is configured such that an exterior can 83 formed by welding a lid body 82 on each end of a cylindrical body 81 accommodates a winding electrode body 84. An electrode terminal mechanism 85 is attached to the lid body 82, and the winding electrode body 84 and the electrode terminal mechanism 85 are connected to each other.
The electrode terminal mechanism 85 includes a positive electrode extending terminal 86 formed of a screw member attached through the lid body 82 of the exterior can 83. The basal end of the positive electrode extending terminal 86 includes a flange portion 86a. An insulating member 87 made of plastic is provided in a gap between the inner circumferential surface of the through hole 82a and the outer circumferential surface of the positive electrode extending terminal 86. The insulating member 87 ensures a sealing property and an electrically insulating property between the lid body 82 and the positive electrode extending terminal 86. A washer 88 fits from the outside of the exterior can 83 onto the positive electrode extending terminal 86, and a first nut 89a and a second nut 89b are threaded to the positive electrode extending terminal 86. The first nut 89a is threaded and the insulating member 87 is sandwiched and pressed between the flange portion 86a of the positive electrode extending terminal 86 and the washer 88. This improves the sealing property of the through hole 82a. 
However, in Patent Document 1, to ensure the sealing property of the through hole 82a, it is necessary to swage the insulating member 87 having a complicated shape and bring the complex surface into close contact with the circumference of the through hole 82a. Since the shape of the insulating member 87 is complicated and the installation of the insulating member 87 is troublesome, the formation of the sealing structure is also troublesome. Patent Document 2 discloses that an O-ring with a simple structure is employed as a sealing member.
As shown in FIG. 14, in a sealed type battery 90 in Patent Document 2, a lid body 91 includes a terminal drawing hole 91a. A positive electrode terminal 92 attached to the terminal drawing hole 91a includes an inner member 93 and an outer member 94. Sealing member compression portions 93a and 94a of the inner member 93 and the outer member 94 include annular grooves 93b and 94b. Sealing members 95 and 96 configured by O-rings are mounted on the corresponding annular grooves 93b and 94b. The inner member 93 and the outer member 94 are welded to each other. This sandwiches the sealing member 95 between the lid body 91 and the sealing member compression portion 93a and the sealing member 96 between the lid body 91 and the sealing member compression portion 94a in the compressed manner. The mounting of the sealing members 95 and 96 on the corresponding annular grooves 93b and 94b limits the positional displacement of the sealing members 95 and 96.
However, in Patent Document 2, it is necessary to precisely mount the sealing member 95 on the annular groove 93b. This results in a poor operability when assembling. In this regard, as in Patent Document 3, a configuration has been proposed in which an O-ring is inserted into a positive electrode terminal and a negative electrode terminal to sandwich the O-ring between the flat surfaces of the lid plate and the seat surface of each terminal.